It is known to produce potassium sulfate and magnesium chloride by means of doubled, i.e., double replacement reaction of potassium chloride and magnesium sulfate. When this doubled reaction is performed in customary manner in aqueous media, the formation of double salts can only be avoided through considerable technical expense.
On the other hand, a process is known from German Offenlegungsschrift DE-OS No. 33 31 416 according to which the potassium chloride is converted into potassium- or sodium sulfate by means of anion exchangers under acid conditions. These techniques can be represented by the following reaction equations: ##EQU1##
Herewith, initially a solution of the desired sulfate is recovered, from which subsequently, by means of additon of potassium- or sodium chloride, the sulfate is salted out. The filtrate separated from the produced crystals is employed for regeneration of the anion exchanger.
The knowledge that the solubility of calcium sulfate is greater in calcium chloride solutions than in water is essential for this technique. Regeneration of the anion exchanger is thereby unexpectedly favored. Indeed, there exists the danger that upon regeneration of the exchanger with the calcium sulfate suspension, the calcium sulfate crystals sedimenting on the exchanger particles will strongly impair the regeneration of the exchanger, and that consequently, the calcium sulfate sedimented on the exchanger particles will be removable only through very great technical expenditure.
Accordingly, there is a genuine need to develop other possibilities for the production of potassium sulfate, with which the disadvantages of the above-mentioned techniques do not occur.